The invention relates to a fuel injection system for mixture-compressing, externally ignited internal combustion engines employing continuous fuel injection into the induction tube. The induction tube contains an air flow measuring member in series with an arbitrarily actuatable throttle butterfly valve. The airflow measuring member operates linearly and its transducer determines the magnitude of an external set-point variable for a linear feedback control loop which includes an electric control amplifier tht changes the position of the armature in an electromagnetic servo-motor. The electromagnetic servo-motor actuates a control slide of a fuel metering valve which meters out a fuel quantity in proportion to the air quantity and which is located in the fuel supply line. The electromagnetic servo-motor sets the control slide of the fuel metering valve by means of a cam plate according to an approximately linear functional relationship.
Fuel injection systems of this type serve the purpose to create automatically a favorable fuel-air mixture for all operational and environmental conditions of the internal combustion engine so that the fuel may be combusted as nearly completely as possible and thus the generation of toxic components in the exhaust gases is either prevented or sharply reduced while the engine maintains the highest possible performance or the least possible fuel consumption.
In a known fuel injection system of this type, the measurement of the air flow rate and the subsequent processing and transmission of the derived signal are substantially linear steps. The set path is transmitted linearly from the servo-motor to the control slide of the fuel metering valve by a three-dimensional cam and any further additive or multiplicative corrections to the injected fuel quantity are made by means of further measuring transducers located in the bridge circuit of the feedback control loop.